This invention relates to an electrostatographic reproducing machine, particularly a xerographic copier, comprising a transfer corotron for transferring a developed electrostatic latent image from an imaging member to a copy sheet, wherein the copy sheets are guided into contact with the imaging member by a guide member adjacent the transfer corotron. The invention further relates to a process unit adapted to be removably mounted in a main assembly of an electrostatographic reproducing machine, wherein the imaging member, the transfer corotron, and the guide member are included in the process unit.
There is a trend nowadays to incorporate the imaging member together with other process means such as a charge corotron, a development device, and a cleaning device in a removable process unit or cassette as described, for example, in U.S. Pat. No. 3,985,436 to Tanaka et al. The use of such a cassette enables the easy replacement of those parts of the xerographic machine which are most likely to deteriorate with use, especially the photoreceptor, but also the development and cleaning systems as well as the charge corotron wire. A further advantage of containing the major xerographic process elements within a cassette is that interchangeable cassettes may be used in a given copying machine to provide different development characteristics or different colored development.
In the art of electrostatographic copying it is known that the electrical conductivity of a paper copy sheet influences the quality of image transfer thereto from the imaging member. If the conductivity of the paper is too high, charges on the paper are able to leak away immediately via those parts of the reproducing machine which are in contact with the sheet, such as the paper guides. Many papers suitable for xerographic copy paper have a conductivity which is satisfactory when the paper is dry, but which becomes too high for effective image transfer when the paper is damp. Under conditions of high ambient relative humidity, copy paper which would otherwise be satisfactory, can absorb moisture to an extent where it becomes so conductive that image transfer is badly impaired.